The invention relates to mordanting substrates and mordanting agents.
Ink jet printing is a non-impact printing system which transfers ink droplets, usually of aqueous ink, from a printhead to a substrate. One important application for ink jet technology is high quality printing, e.g., printing of fine art reproductions or proofs, as ink jet printing is capable of producing near photographic quality imaging due to its use of small dots and high resolution. In high quality printing (and, to a lesser extent, in other ink jet applications) it is important to obtain high color density and limited dot spreading (also referred to as "dot gain").
Dot spreading has been limited by providing an ink-receptive surface layer on the ink jet substrate. These surface layers typically include a film-forming binder, a mordanting agent, silica and/or clays, and other additives. These layers provide a physical barrier between the ink and substrate, with the mordanting agent, often a cationic compound, forming an insoluble complex with the anionic dye to immobilize it while the binder absorbs the solvent. The drying time of inks applied to such substrates is generally limited by the rate of absorption of the solvent by the polymeric binder in combination with the evaporation rate of the solvent.
A wide variety of substrates are used in ink jet printing. Some of these substrates, particularly those used in high quality printing, for example textiles and fine art paper, have specific desirable surface properties (e.g., porosity and texture) which may be unacceptably altered by the application of an ink-receptive surface layer. Without such a surface layer, however, the printed images obtained often exhibit low image density, wide dot spread, loss of sharpness, feathering and show-through.
In the photographic industry, the use of quaternary compounds as mordanting agents for dyes is known. Polymeric quaternaries are mentioned in, e.g., U.S. Pat. Nos. 4,814,255 and 4,463,080, as mordanting materials used in diffusion transfer photography. Mordanting agents have also been used in ink-jet imaging, e.g., as described in U.S. Pat. Nos. 4,554,181, 5,126,010, 5,418,078.